Adverse effects have been classified in many ways. One may divide
1. Predictable (Type A) reactions (mechanism based adverse reactions):-
These are based on the pharmacological properties of the drug, which
means that they are augmented, but qualitatively normal response to the
drug; include side effects, toxic effects and consequences of drug
2. Unpredictable (Type B reactions:- These are based on peculiarities of
the patient and not on drug’s known actions; include allergy. They are less
common, often non-dose related, generally more serious and require
withdrawal of the drug.
SEVERITY OF ADVERSE DRUG REACTIONS
HAS BEEN GRADED AS:
Minor: No therapy, antidote or
prolongation of hospitalization is
Moderate: Requires change in drug
therapy, specific treatment or
prolongs hospital stay by atleast one
Severe: Potentially life-threatening,
causes permanent damage or
requires intensive medical
Lethal: Directly or indirectly
contributes to death of the patient.
Prevention of adverse effects
to drugs Adverse
1. Avoid all inappropriate use of drugs in the context of patient’s clinical condition.
2. Use appropriate dose, route and frequency of drug administration based on patient’s
3. Drug allergy is more common in patients with allergic diseases.
4. Rule out possibility of drug interactions when more than one drug is prescribed.
5. Adopt correct drug administration technique. (e.g. intravenous injection of
6. Carry out appropriate laboratory monitoring.
A drug interaction is a change in the action or side
effects of a drug caused by concomitant
administration with a food, beverage, supplement,
or another drug.
Main factors contributing to drug interactions are-
Multiple drug therapy.
Multiple pharmacological effects of drug.
Multiple diseases / illness.
Poor patient compliance.
Advancing age of patient.
Drug related factors.
Modifications in the effect of a
drug are caused by differences
in the absorption, transport,
distribution, metabolism or
excretion of one or both of the
drugs compared with the
expected behavior of each drug
when taken individually.
When two drugs are used together,
their effects can be additive (the
result is what you expect when you
add together the effect of each
drug taken independently),
synergistic (combining the drugs
leads to a larger effect than
expected), or antagonistic
(combining the drugs leads to a
smaller effect than expected).
The process by which new candidate
medications are discovered is called as
Drug Discovery System.
Preclinical trial - a laboratory test of a
new drug or a series of chemicals, usually
done on animal subjects, to see if the
hoped for treatment really works and if it
is safe to test on humans.
A type of research that studies new
tests and treatments and evaluates
their effects on human health
On Health person
Side effects & Efficacy
Efficacy & Adverse reactions
Post marketing surveillance
In different groups of people
And/or in combination with other treatments
Opportunities for questions should be provided before each vaccination
Must be provided before each dose of vaccine..
Public and private providers.
Available in multiple languages.
Generally, in Phase I trials, the healthy volunteers have been selected.
In this trial, a small number of volunteers (20-50) are selected for the
Generally, this phase has been conducted in order to analyze the
safety, tolerance, pharmacodynamic and pharmacokinetic properties of
These trials are often performed in clinical centres where the subjects
are kept under observations by full–time staff.
Generally, in this study, a group of patients have been administerd the
multiple low doses of the drug, while samples are collected at various
time intervals and analyzed in order to collect information regarding
the processing of drug inside the body.
Later on, the dose of the test drug is increased for further groups upto
a certain level in such studies.
People affected by the
disease and Sample size
is 50-100 patients.
To check the Side effects
The doses used in phase 2
are generally less than the
highest of those used in
Phase II trials are
performed at special
clinical centers like that of
universities and hospitals.
To analyze the efficacy of new drug and its therapeutic effect in
Phase III trials have been considered as the most expensive, time
consuming and difficult to design and run.
Phase III are continued until the regulatory submission is pended at
the appropriate regulatory agency.
To find any Adverse reactions find.
Compared to other treatments. These studies involve 100 to 1,000
Also referred to as “Post marketing surveillance”.
The Phase IV studies can be performed with the help of
regulatory authority or by sponsoring company for finding
a new market of the drug.
Such trails have been designed to find out if any long term
adverse effect over a much large population of patients
for a longer period of time.
Any one seeking treatment for their physician and Watch
drug long term effect.
The information generated by
pharmacovigilance is useful in
educating doctors about ADRs
and in the official regulation of
drug use. It has an important
role in rational use of
medicines, as it provides the
basis for assessing
safety of medicines.
Pharmacovigilance has been
defined by the WHO as the
‘science and activities
relating to the detection,
and prevention of adverse
effects or any other drug
Postmarketing surveillance and other methods of ADR monitoring
such as voluntary reporting by doctors (e.g. yellow card system of
UK). Voluntary reporting depends on the initiative and willingness
of the health professionals. It is minimal in India, while even in the
developed countries only ~10% ADRs are reported voluntarily.
Generally, immediately occurring reactions and those that are
dramatic are reported. Though even rare reactions can be
detected by this method, it does not provide incidence of the
Presentations are tools that can be used as lectures, speeches,
reports, and more. It is mostly presented before an audience
Dissemination of ADR data through ‘drug alerts’, medical letters,’
advisories sent to doctors by pharmaceuticals and regulatory
agencies (such as FDA in USA, committee on safety of medicines in
Changes in the labelling of medicines indicating restrictions in
use or statuary warnings, precautions, or even withdrawal of the
MORE ABOUT PHARMACOVIGILANCE
Pharmacovigilance center's have been
set up in most countries. The Uppsala
Monitoring Centre (Sweden) is the
international collaborating centre. In
India, the national coordinating centre is
located in the All India Institute of
Regional centres are expected to collect
and communicate. ADR data by linking
with medical institutions and
practitioners. The pharmacovigilance
centres are also expected to provide
expertise for assessing causality and
severity of ADRs by using standard
algorithms and rating scales.